A prominent Basque separatist was released from a Spanish prison Tuesday after serving more than six years on terrorism charges for trying to resurrect the banned political wing of the armed group ETA.

Arnaldo Otegi, former leader of the outlawed Batasuna party, was greeted by dozens of supporters chanting "Independence" after he left the prison in the northern city of Logrono.

Speaking to crowd from a platform set up close to the prison, Otegi said, "Today, a political prisoner goes free" and he pledged to continue struggling for peace and independence.

Prior to his imprisonment in 2009, he was considered the political leader of the pro-Basque independence movement.

Batasuna was banned in 2003 on the grounds it was part of ETA, which killed 829 people in a near four-decade campaign for Basque independence. In Otegi's case, the court ruled that he was trying to form a new Batasuna under ETA's orders.

ETA announced a permanent cease-fire in 2011, but hasn't disarmed.

Before his conviction, Otegi had begun to publicly reject the armed campaign as a means to obtain independence, without ever condemning ETA. During his trial, he argued that his group had persuaded the pro-ETA Basque separatist community to reject violence.

But while pro-secession sentiment has surged in Spain's northeastern Catalonia region in recent years, it appears to have lost much impetus in the Basque region and many of its supporters are believed to be switching to the new far-left political group, Podemos.

Otegi is a member of pro-independence party Sortu, an offspring of Batasuna and part of the Bildu coalition that has 21 seats in the 75-seat Basque regional parliament.

There has been speculation that he might present himself as candidate for regional president in local elections later this year although his sentence bans from holding office until 2021.